API Field Updates – Since our Spring Q2 2017 release, activity records retrieved via Marketo’s SOAP or REST APIs now include a 128-character string type field called “marketoGUID”, and the field value matches the value of the “id” field. PLEASE BE ADVISED: Beginning with the Q2 2018 release, the “id” field may no longer be returned as part of these records, and the value of “marketoGUID” string field should be considered the unique ID for retrieved activities. More information may befound online.